1. Field of the Invention
The present invention relates to an integrated circuit and a signal processing apparatus by use thereof.
2. Description of the Related Art
In accordance with a recent progress of electronic technology, there has been a remarkable spread of signal processing apparatuses that have a selling point of portability for handiness of carrying and execute signal processing for desired applications such as portable audio players, cellular phones, portable game machines, and PDAs (Personal Digital Assistants). Such signal processing apparatuses achieve the portability by mounting an internal power source composed of a secondary battery (nickel hydrogen rechargeable battery, lithium ion rechargeable battery, etc.) and a primary battery (alkaline battery, manganese battery, etc.) (see, e.g., Japanese Patent Application Laid-Open Publication No. 2001-184146).
In this connection, long-time execution of the desired application only with a source voltage of the internal power source will necessarily result in an increased power consumption of the internal power source. Accordingly, in consideration of the fact that a large variety of applications are executed for a long time, measures to further reduce the power consumption is essential for the signal processing apparatus and existing measures are insufficient.